Hanna Shoal in Chukchi Sea recently removed from oil leasing by President Obama is biological hot spot for seals and walruses

By Magdalena A K Muir

The Hanna Shoal that US President Obama removed from oil leasing last week has long been known as a biological hot spot in the Arctic Ocean that was not previously protected. The area is so teeming with marine life that walruses are known to make a 300 mile round-trip swim to Hanna Shoal to feast on its abundant clams, snails and worms even when scarcity of sea ice for resting has pushed walruses to shore in the fall.

The northern Chukchi Shelf receivesorganic matter from the productive shelf regions of the North Pacific and from in situ sources of production, including ice algae, sediment microalgae and phytoplankton. This organic carbon, together with l benthic sources of inorganic nitrogen,  contribute to the enormous productivity of this region. The relatively shallow depths (40-55 m) and bottom flow around the shoal facilitate high standing stocks of biota in the benthos, and biological hotspots have been noted along its southeastern and eastern margins.

The Hanna Shoal Ecosystem Study was launched in 2008 is part of a larger Bureau of Ocean Energy Management environmental stewardship program in the US continental shelf regions. The Hanna Shoal team has taken two research cruises aboard the U.S. Coast Guard icebreaking cutter Healy, where scientists removed seafloor sediment and took core samples from  the seafloor to acquire records of long term deposits. Scientists have also used underwater cameras to capture images, trawl gear to analyze fish stocks, and buoys to measure water temperature, salinity, water direction and other characteristics.

Of particular interest is the way the ocean waters, carrying nutrients from the Bering Sea, swing around the shoal, a polygon-shaped feature that rises about 50 feet up from a seafloor that is otherwise about 150 feet deep. Elsewhere tiny organisms in  currents are consumed before they hit the bottom of the sea. At the Hanna Shoal,  plant and animal matter, and marine species that consume them ,are found along the rise of the seafloor. Walruses and seals follow this food. The  structure of the shoal also preserves sea ice late into the melt season.

The four other offshore Arctic areas on Obama’s no-leasing list are the waters near Barrow and Kaktovik, where local residents conduct subsistence hunts; the waters of the Barrow Canyon, a deep formation off Point Barrow that serves as a major conduit for water between the Pacific and the Arctic oceans; and the corridor lying in federal waters between 3 and 25 miles off the Chukchi coastline where bowhead whales regularly migrate.

All these deferral designations were  supported by the North Slope Borough government, the Alaska Eskimo Whaling Commission, and the Inupiat Community of the Arctic Slopes.An Inupiat tribal official said the decision to remove offshore Arctic areas from the auction block was overdue.”They should have this done before they started leasing out the lease areas and messing up all the feeding habitat,” said Doreen Lampe, executive director of the Inupiat Community of the Arctic Slope, an Alaskan tribal government. The no-leasing protections are fair, considering that Endangered Species Act protections have been granted to some animals there and are being considered for others. The concern is whether the no-leasing designations granted by President Obama are permanent enough.

Further information

Hanna Shoal Ecosystem Study


Cruise Report: USCGC Healy 13-01, July 29-August 15, 2013 Chukchi Sea by Lee W. Cooper, Chief Scientist University of Maryland Center for Environmental Science


Alaska Dispatch news article, Chukchi Sea shoal newly closed to oil leasing is well known as biological hot spot